Fumigant compositions and methods

ABSTRACT

Fumigant compositions including hexafluoropropene or 1,1,3,3,3-pentafluoropropene, and methods of making such compositions, are provided herein. The fumigant compositions may be suitable for use as soil fumigant compositions and structural fumigant compositions against a variety of undesirable species such as weeds, nematodes, pathogens, animals and insects. The fumigant compositions also have low toxicity and low Global Warming Potential. In one embodiment, a fumigant composition includes hexafluoropropene, 1,1,3,3,3-pentafluoropropene or a combination thereof. The fumigant composition further includes at least one component selected from methyl iodide, chloropicrin, acrolein, 1,3 dichloropropene, dimethyl disulfide, furfural, propylene oxide metham sodium and combinations thereof. The fumigant composition also includes at least one surfactant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a divisional of U.S. application Ser. No. 13/651,565, filed Oct.15, 2012 and entitled “Fumigation Compositions and Methods,” whichclaims the benefit of U.S. Provisional Application Ser. No. 61/554,623,filed Nov. 2, 2011 entitled “Fumigation Compositions and Methods,” bothof which applications are incorporated by reference herein.

TECHNICAL FIELD

The present technology relates to compositions and formulations for soiland structural fumigation, methods of preparing such formulations, andmethods of fumigating soil and structures with such compositions.

BACKGROUND

Historically, methyl bromide (CH3Br) has been the most widely used andmost universal fumigant in the world. It is known for being extremelyeffective as a herbicide, nematocide, insecticide and fungicide.Consequently, it has been used extensively for soil fumigation, as acommodity quarantine treatment for exports and imports, to control avariety of pests on numerous crops, and as a structural fumigant appliedto building surfaces. However, methyl bromide contributes to thedepletion of the ozone layer in the stratosphere. In accord with theMontreal Protocol, the import and manufacture of methyl bromide in theUnited States and other developed countries was banned in 2005.

Various compounds such as 1,3-dichloropropene, chloropicrin, methamsodium, and methyl iodide have been identified as alternatives to methylbromide. These alternatives are commonly applied as mixtures of two ormore of the individual compounds in order to attempt to produce abroader spectrum product similar to methyl bromide.

As new fumigants are introduced, their global warming potential (GWP) isalso being scrutinized. GWP is a relative measure of how much heat agreenhouse gas traps in the atmosphere. It compares the amount of heattrapped by a certain mass of the gas in question to the amount of heattrapped by a similar mass of carbon dioxide. GWP is calculated over aspecific time interval, commonly 20, 100 or 500 years. GWP is expressedas a factor of carbon dioxide (whose GMP is standardized to 1). Forexample, the 20 year GWP of methane is 56, which means if the sameweights of methane and carbon dioxide were introduced into theatmosphere, that methane will trap 56 times more heat than the carbondioxide over the next 20 years.

BRIEF SUMMARY

Fumigant compositions and methods of making such compositions areprovided herein. The fumigant compositions may be suitable for use assoil fumigant compositions and structural fumigant compositions. In anembodiment, a fumigant composition includes hexafluoropropene,1,1,3,3,3-pentafluoropropene or a combination thereof. The fumigantcomposition further includes at least one component selected from methyliodide, chloropicrin, acrolein, 1,3 dichloropropene, dimethyl disulfide,furfural, propylene oxide metham sodium and combinations thereof. Thefumigant composition also includes at least one surfactant.

In another embodiment, a method of making a fumigant composition isprovided. The method includes combining at least one component selectedfrom methyl iodide, chloropicrin, acrolein, 1,3 dichloropropene,dimethyl disulfide, furfural, propylene oxide metham sodium andcombinations thereof; a surfactant; and at least one ofhexafluoropropene and 1,1,3,3,3-pentafluoropropene in water.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of experimental data.

FIG. 2 is a graphical representation of experimental data.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the integrated circuits or methods for fabricatingintegrated circuits as claimed herein. Furthermore, there is nointention to be bound by any expressed or implied theory presented inthe preceding technical field, background or brief summary, or in thefollowing detailed description.

Embodiments of the present invention include fumigant compositionscomprising an alkylene fluorocarbon including at least one C═CF₂ group.The fluorocarbon may also have a low toxicity and a low GWP. Forexample, the fluorocarbon may have a GWP of less than 1, moreparticularly, less than 0.5.

These fumigant compositions may be used against a variety of differentundesirable species, such as weeds, nematodes or pathogens. In someembodiments, these fumigant compositions may be used against a varietyof different insects, including but not limited to termites,cockroaches, mites and bed bugs. In some embodiments, these fumigantcompositions may be used against animals such as gophers, mice, moles,rats and other rodent pests.

These fumigant compositions may be used in a variety of differenttreatment zones. Broadly, a treatment zone is a surface, space or othervolume that contains undesirable species. In some embodiments, forexample, the treatment zone may be a building such as a warehouse orstore or a vehicle such as a tractor trailer or a rail car.

Fumigant Composition

The fumigant composition includes an alkylene fluorocarbon including atleast one C═CF₂ group. In some embodiments, the alkylene fluorocarbonhas a three carbon backbone. In some instances, smaller alkylenefluorocarbons have been found to polymerize too quickly to be usefulwhile larger alkylene fluorocarbons have been found to be lesseffective.

In some embodiments, the fumigant composition comprises or consistsessentially of hexafluoropropene (“HFP”), or1,1,3,3,3-pentafluoropropene (“1225zc”), which have the followingstructures, respectively:

Hexafluoropropene has a lifetime of only 5.8 days which translates intoa GWP of about 0.25. 1,1,3,3,3-Pentafluoropropene also contains a highlyreactive carbon-carbon double bond and therefore has a GWP of lessthan 1. Both compounds also have negligible ozone depletion potential.

The fluorocarbon may be present in an initial mixture (e.g., prior todiluting into a use solution) in an amount as low as about 1 weightpercent (wt. %), in an amount as low as about 30 wt. %, in an amount aslow as about 40 wt. % or in an amount as low as about 50 wt. %. Thefluorocarbon may be present in an initial mixture, prior to dilution, inan amount as high as about 75 wt. %, in an amount as high as about 85wt. %, in an amount as high as about 95 wt. % or in an amount as high asabout 99 wt. %. The fluorocarbon may further be present within any rangedeliminated by any pair of the foregoing values set forth in thisparagraph. In some examples, the fluorocarbon may have a boiling pointof from about −50° C. to about 50° C.

In addition to the fluorocarbon, the fumigant compositions may alsoinclude at least one additional active ingredient. Suitable actives forthe fumigant compositions include, but are not limited to, methyliodide, chloropicrin, acrolein, 1,3-dichloropropene, dimethyl disulfide,furfural, metham sodium and propylene oxide. In certain embodiments,both HFP and 1225zc may be used with or without additional actives.

Methyl iodide can be present in the initial mixture in any suitableamount, including for example, in an amount as low as about 5 wt. %, inan amount as low as about 15 wt. % or in an amount as low as about 25wt. %. Methyl iodide can be present in the initial mixture in an amountas high as about 50 wt. %, in an amount as high as about 60 wt. % or inan amount as high as about 70 wt. %. Methyl iodide may further bepresent within any range deliminated by any pair of the foregoing valuesset forth in this paragraph.

The fumigant compositions according to embodiments of the presentinvention may further include various additives. In one embodiment, thefumigant composition may include at least one surfactant. Suitablesurfactants for use in fumigant compositions can be ionic surfactants ornon-ionic surfactants. Non-ionic surfactants that can be suitable infumigant compositions include, but are not limited to: Arkopal™ (anonylphenol ethoxylate), Cetomacrogol™ 1000 (a polyethylene glycol),cetostearyl alcohol, cetyl alcohol, cocamide DEA, cocamide MEA, decylglucoside, glyceryl laurate, lauryl glucoside, narrow range ethoxylates,nonoxynols, NP-40, octaethylene glycol monododecyl ether, octylglucoside, oleyl alcohol, pentaethylene glycol, monododecyl ether,poloxamer, polyglycerol polyricinoleate, polysorbate, polysorbate 20,polysorbate 40, polysorbate 60, polysorbate 80, sorbitan monostearate,sorbitan tristearate, stearyl alcohol, Triton™ X-100 (polyethylene oxidechain with an aromatic hydrocarbon group), and Tween™ 80 (apolysorbate). In one specific example, the surfactant can be apolysorbate, which can be polysorbate 20, polysorbate 40, polysorbate 60or polysorbate 80.

The surfactant can be included in an amount that is as low as about 0.1wt. %, in an amount as low as about 3 wt. % or in an amount as low asabout 5 wt. %. The surfactant can be included in an amount that is ashigh as about 15 wt. %, in an amount as high as about 30 wt. % or in anamount as high as about 50 wt. %. The surfactant may further be presentwithin any range deliminated by any pair of the foregoing values setforth in this paragraph.

In some embodiments, the HFP or 1225zc can be diluted with a suitablecarrier solvent that can include at least one C3-C4 hydrofluorocarbonolefin or at least one hydrochlorofluorocarbon olefin which preferablyhave a combination of desirable environmental and functional properties.For example, environmentally, the carrier solvents can have an ozonedepletion potential (ODP) that is zero or about zero. Carrier solventsmay also have a low global warming potential, which can preferably beless than or equal to about 10 relative to CO2. Functionally, carriersolvents are preferably volatile, non-toxic, and non-flammable.Co-solvents for use with this technology include mixtures oftetrafluoropropenes, hexafluorobutenes and chlorotrifluoropropenes. Thecarrier solvents can include an azeotropic or azeotrope-like mixture ofthe at least one C3-C4 hydrofluorocarbon olefin or the at least onehydrochlorofluorocarbon olefin with an organic compound.

The solvent can be included in an amount that is as low as about 1 wt.%. The solvent can be included in an amount as high as about 5 wt. %, inan amount as high as about 50 wt. % or in an amount as high as about 99wt. %. The solvent may further be present within any range deliminatedby any pair of the foregoing values set forth in this paragraph.

For safety purposes, the fumigant composition may include an odorantsuch as banana oil or chloropicrin since certain fluorocarbons includingHFP and 1225zc have no detectable odor.

Application Techniques

The fumigant composition may be applied to soil or structures as part ofan aqueous solution or dispersion. The fumigant composition may beapplied by a number of different procedures that are currently employedfor soil and structural treatments.

In some embodiments, soil fumigant may utilize either shank injection ordrip irrigation. In shank injection fumigant, the chemical fumigant isapplied to the soil by injection through hollow shanks that are pulledthrough the soil, either at shallow depths followed by plastic mulchfilm application, or at deep depths followed by soil compaction.

Application of the chemical fumigant via drip irrigation involvesintroducing and dispersing the chemical fumigant through an existingirrigation system. This provides an advantage of minimizing potentialexposure to workers, as this can be done without workers in the field.

The irrigation system may include one or more dripperlines having aplurality of emitters therein. The emitters, also known as drippers, canbe of any suitable type, including for example pre-punched holes orporous pipe. The emitters can be formed as an integral part of adripperline, or can be separately produced and installed on or in theone or more dripperlines. The emitters can be spaced apart at anysuitable distance, including for example, from about 8 inches apart toabout 24 inches apart (from 200 mm to 600 mm apart).

In some examples, the one or more dripperlines can be placed below thesoil that is to be fumigated. Application of the fumigant composition tothe soil can include providing pressure to cause the fumigantcomposition to flow through the one or more dripperlines and exit theone or more dripperlines through the plurality of emitters to contactand flow into the soil. Alternatively, the fumigants may be applied tothe soil by tractor mounted injectors, manually in canisters or as a gasthrough lay-flat tubing.

The behavior of the fumigant compositions in use is a function of theirwater solubility, volatility, hydrolysis and degradation rates, andtheir sorption to soil organic matter and clay. The physical andchemical properties of the fumigants, such as: water solubility, vaporpressure, boiling point, Henry's constant and half-life in soil, aregood indicators of how each chemical will behave in the soil-air-watersystem. The efficacy of a fumigant correlates to its distributionpatterns in soils and applications that maximize concentrations in thepest-infested zone give better control.

For structural fumigation the chemicals may be heated to a gas beforeintroduction within a building, chamber, vehicle or other space orstructure. The space or structure is preferably sealed with a tarpaulin,fumigant tape or gas impermeable sheeting. In some embodiments,structural fumigant, particularly for rodents, involves sealing thestructure as tightly as possible. In some embodiments, a 2 to 4 milpolyethylene cover may be used to wrap the structure before providingthe fumigant composition. In some embodiments, the structure maysubsequently be aerated to remove the fumigant composition.

Stacked commodities may be treated by draping the commodities with agas-impermeable tarp or sheet that can be sealed to an impermeablesurface (such as a concrete floor) using, for example, sand-filledtubes. After sufficient fumigant composition has been released under thetarp, the space may be aerated to remove remaining fumigant composition.

The fumigant compositions can be prepared by combining the at least onefluorocarbon, the optional active, at least one surfactant and water toform a fumigant composition. The fumigant composition can be a solutionor a homogeneous mixture, which can be formed by mixing the combinedinitial mixture, the at least one surfactant and the water undersuitable conditions. In one example, the fumigant compositions can beformed by mixing the components at a temperature at or below about 60°F. (15.5° C.).

Example 1

Fumigant tests on seeds of the broadleaf species Abutilon theophrastiMedik. and the grass weed species Lolium multiflorum Lam. demonstratethat both HFP and 1125c completely prevented seed germination. Sinceweeds are generally more resistant to fumigant than most nematodes orsoil-borne plant-pathogenic fungi (See Ohr et al., “Methyl Iodide, anOzone-Safe Alternative to Methyl Bromide and a Soil Fumigant,” PlantDisease, July 1996, pp. 731-735; See also Zhang et al., “Effect of SoilPhysical Factors on Methyl Iodide and Methyl Bromide”, Pestic. Sci.1998, pp. 53, 71-79), this result indicates that either of thesechemicals can be employed as a fumigant for the effective control ofplant pathogens, nematodes, bacteria and weeds.

In particular, in 440 mL pressure vessels, fourteen seeds of Abutilontheophrasti Medik. and fifteen seeds of Lolium multiflorum Lam. werethoroughly mixed with 50 mL (approximately 30 grams) of soil and 6 mL ofwater. The filled vessels were kept at room temperature for 20-24 hr toallow the seeds to imbibe water before treatment. The vessels weresealed and evacuated, and then 80 ml, 160 ml and 440 ml respectively ofgaseous 1225zc was added. The vessels were thoroughly mixed and placedhorizontally on the laboratory bench at ambient temperature for twodays. The contents of each bottle were transferred to a plastic sterilePetri dish containing 7 mL of water. The Petri dishes were sealed withparafilm and incubated in the laboratory at ambient temperature. After10 days, the number of germinated seeds was counted. As shown in Table 1below, none of the seeds treated with 1225zc showed any signs ofgermination. The eradication of a broadleaf weed species (Abutilontheophrastic Medik.) and a grass weed species (Lolium multiflorum Lam.)indicates that HFP and 1225zc are suitable as general purpose fumigantcompositions to eradicate weeds, nematodes and soil-borneplant-pathogenic fungi.

TABLE 1 Seeds Germinated Abutilon theophrastic Loliium multiflorumFumigant Medik. Lam. Control 14 15  80 ml 1225zc 0 0 160 ml 1225zc 0 0440 ml 1225zc 0 0

Example 2

The same experiment was performed as described in Example 1 except thathexafluoropropene (HFP) was used as the active fumigant composition. Asshown in Table 2, no germination occurred under any of the experimentalconcentrations.

TABLE 2 Seeds Germinated Abutilon theophrastic Loliium multiflorumFumigant Medik. Lam. Blank 14 15  80 ml HFP 0 0 160 ml HFP 0 0 440 mlHFP 0 0

Example 3

Experimentation was carried out to determine the volatility of aqueousfumigant compositions, both with and without inclusion of a surfactant.In each case, the fluorocarbon was placed in a chilled 500 ml FischerPorter tube that was equipped with a vent to remove any gases. Thevessel was cooled to 0° C. and was charged with varying amounts ofwater, fluorocarbon and surfactant. The temperature was equilibrated to20° C. and the reactor was placed on a balance. The vent tube was openedand the weight loss was recorded every 30 seconds.

In analyzing the effects of adding surfactant to an aqueous solution ofHFP, 10.11 grams of HFP was added to 39.71 grams of water. In a separateexperiment, 9.83 grams of HFP and 4.03 grams of Tween™ 80 were added to40.08 grams of water. FIG. 1 provides a graphical representation of thenumerical data comparing the volatility of an aqueous solution of HFP,both with and without inclusion of the Tween™ 80 nonionic surfactant. Ascan be seen, inclusion of the surfactant provides for longer retentionof the HFP in solution.

In analyzing the effects of adding surfactant to an aqueous solution of1225zc, 10.78 grams of 1225zc were added to 39.69 grams of water. In aseparate experiment, 10.70 grams of 1225zc and 4.08 grams of Tween™ 80were added to 40.15 grams of water. FIG. 2 provides a graphicalrepresentation of the numerical data comparing the volatility of anaqueous solution of 1225zc, both with and without inclusion of theTween™ 80 nonionic surfactant. As can be seen, inclusion of thesurfactant provides for longer retention of the 1225zc in solution.

What is claimed is:
 1. A method of eradicating undesirable species froma treatment zone, the method comprising; contacting the treatment zonewith a fumigant composition comprising: (i) one or more active compoundsand (ii) optionally carrier for said one or more active compounds, saidactive compounds comprising at least about 30% by weight ofhexafluoropropene, 1,1,3,3,3-pentafluoropropene or a combinationthereof.
 2. The method of claim 1 wherein the fumigant compositionfurther comprises at least one component selected from methyl iodide,chloropicrin, acrolein, 1,3 dichloropropene, dimethyl disulfide,furfural, propylene oxide metham sodium and combinations thereof.
 3. Themethod of claim 2 wherein the at least one component compriseschloropicrin.
 4. The method of claim 2 wherein the at least onecomponent comprises acrolein.
 5. The method of claim 2 wherein the atleast one component comprises 1,3 dichloropropene.
 6. The method ofclaim 2 wherein the at least one component comprises dimethyl disulfide.7. The method of claim 2 wherein the at least one component comprisesfurfural.
 8. The method of claim 2 wherein the at least one componentcomprises propylene oxide.
 9. The method of claim 2 wherein the at leastone component comprises metham sodium.
 10. The method of claim 1 whereinsaid fumigant composition consists essentially of hexafluoropropene or1,1,3,3,3-pentafluoropropene, methyl iodide and surfactant.
 11. Themethod of claim 1 wherein said fumigant composition further comprises atleast one odorant.
 12. The method of claim 1 wherein said fumigantcomposition further comprises surfactant.
 13. The method of claim 12wherein the surfactant comprises a polysorbate.
 14. The method of claim1 wherein the fumigant composition is in gaseous form.
 15. The method ofclaim 1 wherein the fumigant composition is in aqueous form.
 16. Amethod of making a fumigant composition, the method comprising combiningat least one component selected from methyl iodide, chloropicrin,acrolein, 1,3 dichloropropene, dimethyl disulfide, furfural, propyleneoxide metham sodium and combinations thereof; a surfactant; and at leastone of hexafluoropropene and 1,1,3,3,3-pentafluoropropene in water. 17.The method of claim 16 wherein the at least one component is methyliodide.
 18. The method of claim 16 wherein the composition is formed asa solution.
 19. The method of claim 16 wherein the composition is formedas a homogeneous mixture.
 20. The method of claim 16 further comprisingmixing the components at a temperature at or below about 15.5° C. 21.The method of claim 2 wherein the at least one component comprisesmethyl iodide.